SpringCloudOpenFeign基本介绍与实现示例

2023-02-21 18:02:16 示例 介绍 SpringCloudOpenFeign

介绍

  在上面一篇介绍Nacos的文章最后,两个服务的相互调用是用的RestTemplate类完成的。但这种方式不是很推荐,更佳的方式是用OpenFeign组件去调用。OpenFeign是官方推出的服务调用和负载均衡组件,基于Ribbon和Hystrix,前身是第一代spring cloud的Feign,对Feign进行了扩展,支持了springMVC的相关注解。

常用注解

  OpenFeign是使用接口+注解实现的,因此了解它的常用注解是必要的,有以下几个:

@EnableFeignClients:在启动类上添加,用于开启OpenFeign功能。当项目启动时,会扫描带有@FeignClient的接口,生成代理类并注册到spring容器

@FeignClient:通知OpenFeign组件对该注解下的接口进行解析,通过动态代理的方式产生实现类,完成服务调用

@RequestMapping:Springmvc中的注解,不过此时该注解表示发起Request请求(默认Get方式)

@GetMapping:SpringMvc中的注解,不过此时该注解表示发起Get请求

@PostMapping:SpringMvc中的注解,不过此时该注解表示发起Post请求

代码实现

  首先得把Nacos启动

  服务提供方,

  bootstrap.yml:

server:
  port: 8083
  servlet:
    context-path: /nacosProvider

spring:
  application:
    name: nacos-provider
  cloud:
    nacos:
      discovery:
        server-addr: 127.0.0.1:8848

  引入依赖:

<dependencies>
    <dependency>
        <groupId>com.alibaba.cloud</groupId>
        <artifactId>spring-cloud-starter-alibaba-nacos-discovery
        </artifactId>
        <version>2.2.0.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
    </dependency>
</dependencies>

  服务方法:

@Controller
@RequestMapping("/provide")
public class ProviderController {
    @RequestMapping("/distribute")
    @ResponseBody
    public String distribute() {
        return "吃鸡胸肉";
    }
    @RequestMapping("/distribute1")
    @ResponseBody
    public String distribute1(String name, Integer age) {
        return "姓名:" + name + ",年龄:" + age;
    }
    @PostMapping("/distribute2")
    @ResponseBody
    public String distribute2(@RequestBody Person p) {
        return "身高:" + p.getHeight() + ",肤色:" + p.getSkin();
    }
}
import lombok.Data;
@Data
public class Person {
    private Integer height;
    private String skin;
}

  服务调用方,

  bootstrap.yml

server:
  port: 8082
  servlet:
    context-path: /nacosInvoke

spring:
  application:
    name: nacos-invoke
  cloud:
    nacos:
      discovery:
        server-addr: 127.0.0.1:8848

  引入依赖:

<dependencies>
    <dependency>
        <groupId>com.alibaba.cloud</groupId>
        <artifactId>spring-cloud-starter-alibaba-nacos-discovery
        </artifactId>
        <version>2.2.0.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</artifactId>
        <version>2.2.0.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
    </dependency>
</dependencies>

  启动类上添加注解:

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;
//开启OpenFeign
@EnableFeignClients
@SpringBootApplication
public class NacosInvokeApplication {
    public static void main(String[] args) {
        SpringApplication.run(NacosConfigApplication.class, args);
    }
}

  创建@FeignClient修饰的接口:

import com.gs.nacos_invoke.dto.Person;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.WEB.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestParam;

@FeignClient(value = "nacos-provider")
public interface InvokeClient {
    @GetMapping("/nacosProvider/provide/distribute")
    String distribute();
    @GetMapping("/nacosProvider/provide/distribute1")
    String distribute1(@RequestParam("name") String name, 
    @RequestParam("age") Integer age);
    @PostMapping("/nacosProvider/provide/distribute2")
    String distribute2(@RequestBody Person p);
}

  Person类(服务调用方再创建一个,不是同一个):

import lombok.Data;
@Data
public class Person {
    private Integer height;
    private String skin;
}

  编写控制器,使用接口请求提供方的服务:

import com.gs.nacos_invoke.dto.Person;
import com.gs.nacos_config.feign.InvokeClient;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
@Controller
@RequestMapping("/user")
public class UserController {
    @Autowired
    private InvokeClient invokeClient;
    @GetMapping("/invoke")
    public void invoke(String name, Integer age) {
        String str = invokeClient.distribute();
        System.out.println(str);
    }
    @GetMapping("/invoke1")
    public void invoke1() {
        String str = invokeClient.distribute1("coder", 20);
        System.out.println(str);
    }
    @GetMapping("/invoke2")
    public void invoke2() {
        Person p = new Person();
        p.setHeight(183);
        p.setSkin("黄皮肤");
        String s = invokeClient.distribute2(p);
        System.out.println(s);
    }
}

注意事项

  OpenFeign是基于Ribbon的,所以它默认是负载均衡的。其次,它也是基于Hystrix的,有超时降级的处理:默认服务提供方的接口超时时间是1s,超过1s服务调用方会报错。1s是可以配置的,按照业务需要调整。@FeignClient注解有个fallback属性,当该属性有值时,服务提供方超时,会返回程序所指定的降级值。

  服务调用方,bootstrap.yml添加(更规范的做法是引入spring-cloud-starter-alibaba-nacos-config依赖,nacos中新建配置,然后在这个配置中添加):

feign:
  hystrix:
    enabled: true
ribbon:
    # 请求连接的超时时间
    ConnectionTimeout: 3000
    # 请求处理的超时时间
    ReadTimeout: 3000

hystrix:
    command:
        default:
            execution:
                isolation:
                    thread:
                        timeoutInMilliseconds: 3000

  接口修改为:

import com.gs.nacos_invoke.dto.Person;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestParam;
@FeignClient(value = "nacos-provider",
        fallback = InvokeClientFallback.class)
public interface InvokeClient {
    @GetMapping("/nacosProvider/provide/distribute")
    String distribute();
    @GetMapping("/nacosProvider/provide/distribute1")
    String distribute1(@RequestParam("name") String name, 
    @RequestParam("age") Integer age);
    @PostMapping("/nacosProvider/provide/distribute2")
    String distribute2(@RequestBody Person p);
}

  fallback指定的类:

import com.gs.nacos_invoke.dto.Person;
import org.springframework.stereotype.Component;
@Component
public class InvokeClientFallback implements InvokeClient {
    @Override
    public String distribute() {
        return "超时3s";
    }
    @Override
    public String distribute1(String name, Integer age) {
        return "超时3s";
    }
    @Override
    public String distribute2(Person p) {
        return "超时3s";
    }
}

  服务提供方ProviderController类的方法中,加入Thread.sleep(4000);或者throw new RuntimeException("抛异常");来触发降级(抛出未捕获的异常也能触发)。

到此这篇关于SpringCloud OpenFeign基本介绍与实现示例的文章就介绍到这了,更多相关SprinGCloud OpenFeign内容请搜索以前的文章或继续浏览下面的相关文章希望大家以后多多支持!

相关文章